The invention deals with studies of properties of liquids which can be applied to numerous industries such as oil, gas and chemical industry.
The volume thermal expansion coefficient (VTEC or α) is a physics value describing a relative change in a body volume due to temperature increase by one degree at a constant pressure:
      α    =                  1        V            ⁢                        (                                    ⅆ              V                                      ⅆ              T                                )                p              ,where V is the volume, T is the temperature, and p is the pressure. VTEC has a dimension inverse to temperature.
VTEC is an important thermodynamic parameter describing properties of liquids. This parameter is often required to describe models of liquids, for example, to simulate properties of oil and gas deposits in oil industry. For a given liquid VTEC depends on temperature and pressure. At the same time, VTEC measurements are often carried out at atmospheric pressure when the temperature does not match the required value.
Various techniques are used to measure VTEC: measurements of density of a liquid at different temperatures and pressures with subsequent interpretation of results obtained (Calado, J. C. G.; Clancy, P. Heintz, A. Streett, W. B. Experimental and theoretical study of the equation of state of liquid ethylene. J. Chem. Eng. Data 1982, 27, 376-385), measurements of sound velocity in a liquid (Davis, L. A.; Gordon, R. B. Compression of mercury at high pressure, J. Chem. Phys. 1967, 46 (7), 2650-2660). The above methods have low accuracy.
More precise information on VTEC can be obtained from measurements using a differential scanning calorimeter (DSC).
U.S. Pat. No. 6,869,214 B2 describes a method of measuring VTEC in a liquid solution using DSC. The method does not take into account influence of thermal effects associated with expanding material of a calorimeter cell during VTEC measurements; change of the cell effective volume when the pressure changes during VTEC measurements is also not taken into account, which reduces accuracy of VTEC obtained.